Why I built my own browser for AI coding agents in 2026

At my day job we needed manual testing for our platform: acting like a real user under different conditions, such as a slow network, different screen sizes, and signed-in flows. It is 2026, so the obvious idea was to let an AI agent walk through the site and check it instead of a person.

We looked at the existing tools. There are many, and none of them fit what we needed. So, oddly enough for 2026, I ended up writing my own app: a separate, visible browser that an AI agent drives. That became Hronaut.

This post covers what the existing tools were missing, how the browser is built, and what I learned along the way.

We wanted a browser where the agent checks the site like a real user, while a human stays in control. That gave us a list of requirements:

Each existing option covered some of these, never all at once. Playwright MCP is a great automation tool, but its browser is designed for a robot, not for working next to a human. Chrome extensions hand the agent your real browser with all your personal accounts. Cloud browsers are great for scale, but they can't simply reach a local dev server.

On our platform, this got very concrete. With Playwright MCP, the browser closed together with the agent session, so after every restart we signed in again and reopened the pages under test. When the agent ran in a browser nobody was watching, the only way to know what it had done was to read the logs afterwards. Sometimes it reported "done" while it was actually stuck on the login page or looking at an empty page. Trying a Chrome extension meant handing the agent my real work browser, with my email and personal accounts, and I wasn't willing to do that. And a cloud browser couldn't open localhost or our internal staging environment at all.

Hronaut is an Electron desktop app for Windows, macOS, and Linux. Inside it runs an MCP server (Streamable HTTP transport) that listens only on 127.0.0.1 (port 47812 by default). The agent connects to it like any other MCP server and gets tools to open a tab, navigate, click, type, read the page, and take a screenshot.

My main takeaway: an AI agent in a browser needs more than access to pages. It needs a person nearby who can see what's happening and step in. That's what Hronaut is for.

How do you give your agent a browser? Do you trust it with your own Chrome, keep a separate profile, or not let it in at all? I'd love to hear your stories and criticism in the comments, and I'll answer questions about how Hronaut works myself.

Disclosure: I'm the developer of Hronaut. This article was written with the help of AI.